resolved.conf

title: resolved.conf(5)

text:
# resolved.conf(5)

## NAME
resolved.conf, resolved.conf.d - Network Name Resolution configuration files

## SYNOPSIS
/etc/systemd/resolved.conf

/etc/systemd/resolved.conf.d/*.conf

/run/systemd/resolved.conf.d/*.conf

/lib/systemd/resolved.conf.d/*.conf

## DESCRIPTION
These configuration files control local DNS and LLMNR name resolution.

## CONFIGURATION DIRECTORIES AND PRECEDENCE
The default configuration is set during compilation, so configuration is only needed when it is necessary to deviate from those defaults. Initially, the main configuration file in /etc/systemd/ contains commented out entries showing the defaults as a guide to the administrator. Local overrides can be created by editing this file or by creating drop-ins, as described below. Using drop-ins for local configuration is recommended over modifications to the main configuration file.

In addition to the "main" configuration file, drop-in configuration snippets are read from /lib/systemd/*.conf.d/, /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/. Those drop-ins have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files.

When packages need to customize the configuration, they can install drop-ins under /usr/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. Drop-ins have to be used to override package drop-ins, since the main configuration file has lower precedence. It is recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering of the files.

To disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file.

## OPTIONS
The following options are available in the [Resolve] section:

DNS=

A space-separated list of IPv4 and IPv6 addresses to use as system DNS servers. Each address can optionally take a port number separated with ":", a network interface name or index separated with "%", and a Server Name Indication (SNI) separated with "#". When IPv6 address is specified with a port number, then the address must be in the square brackets. That is, the acceptable full formats are "111.222.333.444:9953%ifname#example.com" for IPv4 and "[1111:2222::3333]:9953%ifname#example.com" for IPv6. DNS requests are sent to one of the listed DNS servers in parallel to suitable per-link DNS servers acquired from systemd-networkd.service(8) or set at runtime by external applications. For compatibility reasons, if this setting is not specified, the DNS servers listed in /etc/resolv.conf are used instead, if that file exists and any servers are configured in it. This setting defaults to the empty list.

FallbackDNS=

A space-separated list of IPv4 and IPv6 addresses to use as the fallback DNS servers. Please see DNS= for acceptable format of addresses. Any per-link DNS servers obtained from systemd-networkd.service(8) take precedence over this setting, as do any servers set via DNS= above or /etc/resolv.conf. This setting is hence only used if no other DNS server information is known. If this option is not given, a compiled-in list of DNS servers is used instead.

Domains=

A space-separated list of domains optionally prefixed with "~", used for two distinct purposes described below. Defaults to the empty list. Any domains not prefixed with "~" are used as search suffixes when resolving single-label hostnames (domain names which contain no dot), in order to qualify them into fully-qualified domain names (FQDNs). These "search domains" are strictly processed in the order they are specified in, until the name with the suffix appended is found. For compatibility reasons, if this setting is not specified, the search domains listed in /etc/resolv.conf with the search keyword are used instead, if that file exists and any domains are configured in it.

The domains prefixed with "~" are called "routing domains". All domains listed here (both search domains and routing domains after removing the "~" prefix) define a search path that preferably directs DNS queries to this interface. This search path has an effect only when suitable per-link DNS servers are known. Such servers may be defined through the DNS= setting (see above) and dynamically at run time, for example from DHCP leases. If no per-link DNS servers are known, routing domains have no effect.

Use the construct "~." (which is composed from "~" to indicate a routing domain and "." to indicate the DNS root domain that is the implied suffix of all DNS domains) to use the DNS servers defined for this link preferably for all domains.

LLMNR=

Takes a boolean argument or "resolve". Controls Link-Local Multicast Name Resolution support (RFC 4795[1]) on the local host. If true, enables full LLMNR responder and resolver support. If false, disables both. If set to "resolve", only resolution support is enabled, but responding is disabled. Note that systemd-networkd.service(8) also maintains per-link LLMNR settings. LLMNR will be enabled on a link only if the per-link and the global setting is on.

MulticastDNS=

Takes a boolean argument or "resolve". Controls Multicast DNS support (RFC 6762[2]) on the local host. If true, enables full Multicast DNS responder and resolver support. If false, disables both. If set to "resolve", only resolution support is enabled, but responding is disabled. Note that systemd-networkd.service(8) also maintains per-link Multicast DNS settings. Multicast DNS will be enabled on a link only if the per-link and the global setting is on.

DNSSEC=

Takes a boolean argument or "allow-downgrade". If true all DNS lookups are DNSSEC-validated locally (excluding LLMNR and Multicast DNS). If the response to a lookup request is detected to be invalid a lookup failure is returned to applications. Note that this mode requires a DNS server that supports DNSSEC. If the DNS server does not properly support DNSSEC all validations will fail. If set to "allow-downgrade" DNSSEC validation is attempted, but if the server does not support DNSSEC properly, DNSSEC mode is automatically disabled. Note that this mode makes DNSSEC validation vulnerable to "downgrade" attacks, where an attacker might be able to trigger a downgrade to non-DNSSEC mode by synthesizing a DNS response that suggests DNSSEC was not supported. If set to false, DNS lookups are not DNSSEC validated. Note that DNSSEC validation requires retrieval of additional DNS data, and thus results in a small DNS look-up time penalty.

DNSSEC requires knowledge of "trust anchors" to prove data integrity. The trust anchor for the Internet root domain is built into the resolver, additional trust anchors may be defined with dnssec-trust-anchors.d(5). Trust anchors may change at regular intervals, and old trust anchors may be revoked. In such a case DNSSEC validation is not possible until new trust anchors are configured locally or the resolver software package is updated with the new root trust anchor. In effect, when the built-in trust anchor is revoked and DNSSEC= is true, all further lookups will fail, as it cannot be proved anymore whether lookups are correctly signed, or validly unsigned. If DNSSEC= is set to "allow-downgrade" the resolver will automatically turn off DNSSEC validation in such a case.

Client programs looking up DNS data will be informed whether lookups could be verified using DNSSEC, or whether the returned data could not be verified (either because the data was found unsigned in the DNS, or the DNS server did not support DNSSEC or no appropriate trust anchors were known). In the latter case it is assumed that client programs employ a secondary scheme to validate the returned DNS data, should this be required.

It is recommended to set DNSSEC= to true on systems where it is known that the DNS server supports DNSSEC correctly, and where software or trust anchor updates happen regularly. On other systems it is recommended to set DNSSEC= to "allow-downgrade".

In addition to this global DNSSEC setting systemd-networkd.service(8) also maintains per-link DNSSEC settings. For system DNS servers (see above), only the global DNSSEC setting is in effect. For per-link DNS servers the per-link setting is in effect, unless it is unset in which case the global setting is used instead.

Site-private DNS zones generally conflict with DNSSEC operation, unless a negative (if the private zone is not signed) or positive (if the private zone is signed) trust anchor is configured for them. If "allow-downgrade" mode is selected, it is attempted to detect site-private DNS zones using top-level domains (TLDs) that are not known by the DNS root server. This logic does not work in all private zone setups.

Defaults to "no".

DNSOverTLS=

Takes a boolean argument or "opportunistic". If true all connections to the server will be encrypted. Note that this mode requires a DNS server that supports DNS-over-TLS and has a valid certificate. If the hostname was specified in DNS= by using the format format "address#server_name" it is used to validate its certificate and also to enable Server Name Indication (SNI) when opening a TLS connection. Otherwise the certificate is checked against the server's IP. If the DNS server does not support DNS-over-TLS all DNS requests will fail. When set to "opportunistic" DNS request are attempted to send encrypted with DNS-over-TLS. If the DNS server does not support TLS, DNS-over-TLS is disabled. Note that this mode makes DNS-over-TLS vulnerable to "downgrade" attacks, where an attacker might be able to trigger a downgrade to non-encrypted mode by synthesizing a response that suggests DNS-over-TLS was not supported. If set to false, DNS lookups are send over UDP.

Note that DNS-over-TLS requires additional data to be send for setting up an encrypted connection, and thus results in a small DNS look-up time penalty.

Note that in "opportunistic" mode the resolver is not capable of authenticating the server, so it is vulnerable to "man-in-the-middle" attacks.

In addition to this global DNSOverTLS= setting systemd-networkd.service(8) also maintains per-link DNSOverTLS= settings. For system DNS servers (see above), only the global DNSOverTLS= setting is in effect. For per-link DNS servers the per-link setting is in effect, unless it is unset in which case the global setting is used instead.

Defaults to "no".

Cache=

Takes a boolean or "no-negative" as argument. If "yes" (the default), resolving a domain name which already got queried earlier will return the previous result as long as it is still valid, and thus does not result in a new network request. Be aware that turning off caching comes at a performance penalty, which is particularly high when DNSSEC is used. If "no-negative", only positive answers are cached. Note that caching is turned off by default for host-local DNS servers. See CacheFromLocalhost= for details.

CacheFromLocalhost=

Takes a boolean as argument. If "no" (the default), and response cames from host-local IP address (such as 127.0.0.1 or ::1), the result wouldn't be cached in order to avoid potential duplicate local caching.

DNSStubListener=

Takes a boolean argument or one of "udp" and "tcp". If "udp", a DNS stub resolver will listen for UDP requests on address 127.0.0.53 port 53. If "tcp", the stub will listen for TCP requests on the same address and port. If "yes" (the default), the stub listens for both UDP and TCP requests. If "no", the stub listener is disabled. Note that the DNS stub listener is turned off implicitly when its listening address and port are already in use.

DNSStubListenerExtra=

Takes an IPv4 or IPv6 address to listen on. The address may be optionally prefixed with a protocol name ("udp" or "tcp") separated with ":". If the protocol is not specified, the service will listen on both UDP and TCP. It may be also optionally suffixed by a numeric port number with separator ":". When an IPv6 address is specified with a port number, then the address must be in the square brackets. If the port is not specified, then the service uses port 53. Note that this is independent of the primary DNS stub configured with DNSStubListener=, and only configures additional sockets to listen on. This option can be specified multiple times. If an empty string is assigned, then the all previous assignments are cleared. Defaults to unset. Examples:

```
DNSStubListenerExtra=192.168.10.10
DNSStubListenerExtra=2001:db8:0:f102::10
DNSStubListenerExtra=192.168.10.11:9953
DNSStubListenerExtra=[2001:db8:0:f102::11]:9953
DNSStubListenerExtra=tcp:192.168.10.12
DNSStubListenerExtra=udp:2001:db8:0:f102::12
DNSStubListenerExtra=tcp:192.168.10.13:9953
DNSStubListenerExtra=udp:[2001:db8:0:f102::13]:9953
```

ReadEtcHosts=

Takes a boolean argument. If "yes" (the default), systemd-resolved will read /etc/hosts, and try to resolve hosts or address by using the entries in the file before sending query to DNS servers.

ResolveUnicastSingleLabel=

Takes a boolean argument. When false (the default), systemd-resolved will not resolve A and AAAA queries for single-label names over classic DNS. Note that such names may still be resolved if search domains are specified (see Domains= above), or using other mechanisms, in particular via LLMNR or from /etc/hosts. When true, queries for single-label names will be forwarded to global DNS servers even if no search domains are defined. This option is provided for compatibility with configurations where public DNS servers are not used. Forwarding single-label names to servers not under your control is not standard-conformant, see IAB Statement[3], and may create a privacy and security risk.

## SEE ALSO
systemd(1), systemd-resolved.service(8), systemd-networkd.service(8), dnssec-trust-anchors.d(5), resolv.conf(5)

## NOTES
1.

RFC 4795

https://tools.ietf.org/html/rfc4795

2.

RFC 6762

https://tools.ietf.org/html/rfc6762

3.

IAB Statement

https://www.iab.org/documents/correspondence-reports-documents/2013-2/iab-statement-dotless-domains-considered-harmful/


systemd.dnssd

package: systemd-networkd

title: systemd.dnssd(5)

summary: DNS\-SD configuration

text:
# systemd.dnssd(5)

## NAME
systemd.dnssd - DNS-SD configuration

## SYNOPSIS
network_service.dnssd

## DESCRIPTION
DNS-SD setup is performed by systemd-resolved(8).

The main network service file must have the extension .dnssd; other extensions are ignored.

The .dnssd files are read from the files located in the system network directories /lib/systemd/dnssd and /usr/local/lib/systemd/dnssd, the volatile runtime network directory /run/systemd/dnssd and the local administration network directory /etc/systemd/dnssd. All configuration files are collectively sorted and processed in lexical order, regardless of the directories in which they live. However, files with identical filenames replace each other. Files in /etc/ have the highest priority, files in /run/ take precedence over files with the same name in /lib/. This can be used to override a system-supplied configuration file with a local file if needed.

Along with the network service file foo.dnssd, a "drop-in" directory foo.dnssd.d/ may exist. All files with the suffix ".conf" from this directory will be parsed after the file itself is parsed. This is useful to alter or add configuration settings, without having to modify the main configuration file. Each drop-in file must have appropriate section headers.

In addition to /etc/systemd/dnssd, drop-in ".d" directories can be placed in /lib/systemd/dnssd or /run/systemd/dnssd directories. Drop-in files in /etc/ take precedence over those in /run/ which in turn take precedence over those in /lib/ or /usr/local/lib. Drop-in files under any of these directories take precedence over the main network service file wherever located.

## [SERVICE] SECTION OPTIONS
The network service file contains a [Service] section, which specifies a discoverable network service announced in a local network with Multicast DNS broadcasts.

Name=

An instance name of the network service as defined in the section 4.1.1 of RFC 6763[1], e.g. "webserver". The option supports simple specifier expansion. The following expansions are understood:

Table 1. Specifiers available

Specifier

Meaning

Details

"%a"

Architecture

A short string identifying the architecture of the local system. A string such as x86, x86-64 or arm64. See the architectures defined for ConditionArchitecture= in systemd.unit(5) for a full list.

"%A"

Operating system image version

The operating system image version identifier of the running system, as read from the IMAGE_VERSION= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information.

"%b"

Boot ID

The boot ID of the running system, formatted as string. See random(4) for more information.

"%B"

Operating system build ID

The operating system build identifier of the running system, as read from the BUILD_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information.

"%H"

Host name

The hostname of the running system.

"%m"

Machine ID

The machine ID of the running system, formatted as string. See machine-id(5) for more information.

"%M"

Operating system image identifier

The operating system image identifier of the running system, as read from the IMAGE_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information.

"%o"

Operating system ID

The operating system identifier of the running system, as read from the ID= field of /etc/os-release. See os-release(5) for more information.

"%v"

Kernel release

Identical to uname -r output.

"%w"

Operating system version ID

The operating system version identifier of the running system, as read from the VERSION_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information.

"%W"

Operating system variant ID

The operating system variant identifier of the running system, as read from the VARIANT_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information.

"%%"

Single percent sign

Use "%%" in place of "%" to specify a single percent sign.

Type=

A type of the network service as defined in the section 4.1.2 of RFC 6763[1], e.g. "_http._tcp".

Port=

An IP port number of the network service.

Priority=

A priority number set in SRV resource records corresponding to the network service.

Weight=

A weight number set in SRV resource records corresponding to the network service.

TxtText=

A whitespace-separated list of arbitrary key/value pairs conveying additional information about the named service in the corresponding TXT resource record, e.g. "path=/portal/index.html". Keys and values can contain C-style escape sequences which get translated upon reading configuration files. This option together with TxtData= may be specified more than once, in which case multiple TXT resource records will be created for the service. If the empty string is assigned to this option, the list is reset and all prior assignments will have no effect.

TxtData=

A whitespace-separated list of arbitrary key/value pairs conveying additional information about the named service in the corresponding TXT resource record where values are base64-encoded string representing any binary data, e.g. "data=YW55IGJpbmFyeSBkYXRhCg==". Keys can contain C-style escape sequences which get translated upon reading configuration files. This option together with TxtText= may be specified more than once, in which case multiple TXT resource records will be created for the service. If the empty string is assigned to this option, the list is reset and all prior assignments will have no effect.

## EXAMPLES
Example 1. HTTP service

```
# /etc/systemd/dnssd/http.dnssd
[Service]
Name=%H
Type=_http._tcp
Port=80
TxtText=path=/stats/index.html t=temperature_sensor
```

This makes the http server running on the host discoverable in the local network given MulticastDNS is enabled on the network interface.

Now the utility "resolvectl" should be able to resolve the service to the host's name:

```
$ resolvectl service meteo._http._tcp.local
meteo._http._tcp.local: meteo.local:80 [priority=0, weight=0]

                        169.254.208.106%senp0s21f0u2u4

                        fe80::213:3bff:fe49:8aa%senp0s21f0u2u4

                        path=/stats/index.html

                        t=temperature_sensor

                        (meteo/_http._tcp/local)
-- Information acquired via protocol mDNS/IPv6 in 4.0ms.
-- Data is authenticated: yes
```

"Avahi" running on a different host in the same local network should see the service as well:

```
$ avahi-browse -a -r
+ enp3s0 IPv6 meteo                                         Web Site             local
+ enp3s0 IPv4 meteo                                         Web Site             local
= enp3s0 IPv6 meteo                                         Web Site             local

   hostname = [meteo.local]

   address = [fe80::213:3bff:fe49:8aa]

   port = [80]

   txt = ["path=/stats/index.html" "t=temperature_sensor"]
= enp3s0 IPv4 meteo                                         Web Site             local

   hostname = [meteo.local]

   address = [169.254.208.106]

   port = [80]

   txt = ["path=/stats/index.html" "t=temperature_sensor"]
```

## SEE ALSO
systemd(1), systemd-resolved.service(8), resolvectl(1)

## NOTES
1.

RFC 6763

https://tools.ietf.org/html/rfc6763


systemd.netdev

title: systemd.netdev(5)

summary: Virtual Network Device configuration

text:
# systemd.netdev(5)

## NAME
systemd.netdev - Virtual Network Device configuration

## SYNOPSIS
netdev.netdev

## DESCRIPTION
A plain ini-style text file that encodes configuration about a virtual network device, used by systemd-networkd(8). See systemd.syntax(7) for a general description of the syntax.

The main Virtual Network Device file must have the extension .netdev; other extensions are ignored. Virtual network devices are created as soon as networkd is started. If a netdev with the specified name already exists, networkd will use that as-is rather than create its own. Note that the settings of the pre-existing netdev will not be changed by networkd.

The .netdev files are read from the files located in the system network directory /lib/systemd/network, the volatile runtime network directory /run/systemd/network and the local administration network directory /etc/systemd/network. All configuration files are collectively sorted and processed in lexical order, regardless of the directories in which they live. However, files with identical filenames replace each other. Files in /etc/ have the highest priority, files in /run/ take precedence over files with the same name in /lib/. This can be used to override a system-supplied configuration file with a local file if needed. As a special case, an empty file (file size 0) or symlink with the same name pointing to /dev/null disables the configuration file entirely (it is "masked").

Along with the netdev file foo.netdev, a "drop-in" directory foo.netdev.d/ may exist. All files with the suffix ".conf" from this directory will be merged in the alphanumeric order and parsed after the main file itself has been parsed. This is useful to alter or add configuration settings, without having to modify the main configuration file. Each drop-in file must have appropriate section headers.

In addition to /etc/systemd/network, drop-in ".d" directories can be placed in /lib/systemd/network or /run/systemd/network directories. Drop-in files in /etc/ take precedence over those in /run/ which in turn take precedence over those in /lib/. Drop-in files under any of these directories take precedence over the main netdev file wherever located. (Of course, since /run/ is temporary and /lib/ is for vendors, it is unlikely drop-ins should be used in either of those places.)

## SUPPORTED NETDEV KINDS
The following kinds of virtual network devices may be configured in .netdev files:

Table 1. Supported kinds of virtual network devices

Kind

Description

bond

A bond device is an aggregation of all its slave devices. See Linux Ethernet Bonding Driver HOWTO[1] for details.

bridge

A bridge device is a software switch, and each of its slave devices and the bridge itself are ports of the switch.

dummy

A dummy device drops all packets sent to it.

gre

A Level 3 GRE tunnel over IPv4. See RFC 2784[2] for details.

gretap

A Level 2 GRE tunnel over IPv4.

erspan

ERSPAN mirrors traffic on one or more source ports and delivers the mirrored traffic to one or more destination ports on another switch. The traffic is encapsulated in generic routing encapsulation (GRE) and is therefore routable across a layer 3 network between the source switch and the destination switch.

ip6gre

A Level 3 GRE tunnel over IPv6.

ip6tnl

An IPv4 or IPv6 tunnel over IPv6

ip6gretap

A Level 2 GRE tunnel over IPv6.

ipip

An IPv4 over IPv4 tunnel.

ipvlan

An IPVLAN device is a stacked device which receives packets from its underlying device based on IP address filtering.

ipvtap

An IPVTAP device is a stacked device which receives packets from its underlying device based on IP address filtering and can be accessed using the tap user space interface.

macvlan

A macvlan device is a stacked device which receives packets from its underlying device based on MAC address filtering.

macvtap

A macvtap device is a stacked device which receives packets from its underlying device based on MAC address filtering.

sit

An IPv6 over IPv4 tunnel.

tap

A persistent Level 2 tunnel between a network device and a device node.

tun

A persistent Level 3 tunnel between a network device and a device node.

veth

An Ethernet tunnel between a pair of network devices.

vlan

A VLAN is a stacked device which receives packets from its underlying device based on VLAN tagging. See IEEE 802.1Q[3] for details.

vti

An IPv4 over IPSec tunnel.

vti6

An IPv6 over IPSec tunnel.

vxlan

A virtual extensible LAN (vxlan), for connecting Cloud computing deployments.

geneve

A GEneric NEtwork Virtualization Encapsulation (GENEVE) netdev driver.

l2tp

A Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs) or as part of the delivery of services by ISPs. It does not provide any encryption or confidentiality by itself

macsec

Media Access Control Security (MACsec) is an 802.1AE IEEE industry-standard security technology that provides secure communication for all traffic on Ethernet links. MACsec provides point-to-point security on Ethernet links between directly connected nodes and is capable of identifying and preventing most security threats.

vrf

A Virtual Routing and Forwarding (VRF[4]) interface to create separate routing and forwarding domains.

vcan

The virtual CAN driver (vcan). Similar to the network loopback devices, vcan offers a virtual local CAN interface.

vxcan

The virtual CAN tunnel driver (vxcan). Similar to the virtual ethernet driver veth, vxcan implements a local CAN traffic tunnel between two virtual CAN network devices. When creating a vxcan, two vxcan devices are created as pair. When one end receives the packet it appears on its pair and vice versa. The vxcan can be used for cross namespace communication.

wireguard

WireGuard Secure Network Tunnel.

nlmon

A Netlink monitor device. Use an nlmon device when you want to monitor system Netlink messages.

fou

Foo-over-UDP tunneling.

xfrm

A virtual tunnel interface like vti/vti6 but with several advantages.

ifb

The Intermediate Functional Block (ifb) pseudo network interface acts as a QoS concentrator for multiple different sources of traffic.

bareudp

Bare UDP tunnels provide a generic L3 encapsulation support for tunnelling different L3 protocols like MPLS, IP etc. inside of an UDP tunnel.

batadv

B.A.T.M.A.N. Advanced[5] is a routing protocol for multi-hop mobile ad-hoc networks which operates on layer 2.

## [MATCH] SECTION OPTIONS
A virtual network device is only created if the [Match] section matches the current environment, or if the section is empty. The following keys are accepted:

Host=

Matches against the hostname or machine ID of the host. See "ConditionHost=" in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, then previously assigned value is cleared.

Virtualization=

Checks whether the system is executed in a virtualized environment and optionally test whether it is a specific implementation. See "ConditionVirtualization=" in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, then previously assigned value is cleared.

KernelCommandLine=

Checks whether a specific kernel command line option is set. See "ConditionKernelCommandLine=" in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, then previously assigned value is cleared.

KernelVersion=

Checks whether the kernel version (as reported by uname -r) matches a certain expression. See "ConditionKernelVersion=" in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, then previously assigned value is cleared.

Architecture=

Checks whether the system is running on a specific architecture. See "ConditionArchitecture=" in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, then previously assigned value is cleared.

Firmware=

Checks whether the system is running on a machine with the specified firmware. See "ConditionFirmware=" in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, then previously assigned value is cleared.

## [NETDEV] SECTION OPTIONS
The [NetDev] section accepts the following keys:

Description=

A free-form description of the netdev.

Name=

The interface name used when creating the netdev. This setting is compulsory.

Kind=

The netdev kind. This setting is compulsory. See the "Supported netdev kinds" section for the valid keys.

MTUBytes=

The maximum transmission unit in bytes to set for the device. The usual suffixes K, M, G are supported and are understood to the base of 1024. For "tun" or "tap" devices, MTUBytes= setting is not currently supported in [NetDev] section. Please specify it in [Link] section of corresponding systemd.network(5) files.

MACAddress=

The MAC address to use for the device. For "tun" or "tap" devices, setting MACAddress= in the [NetDev] section is not supported. Please specify it in [Link] section of the corresponding systemd.network(5) file. If this option is not set, "vlan" devices inherit the MAC address of the physical interface. For other kind of netdevs, if this option is not set, then MAC address is generated based on the interface name and the machine-id(5).

## [BRIDGE] SECTION OPTIONS
The [Bridge] section only applies for netdevs of kind "bridge", and accepts the following keys:

HelloTimeSec=

HelloTimeSec specifies the number of seconds between two hello packets sent out by the root bridge and the designated bridges. Hello packets are used to communicate information about the topology throughout the entire bridged local area network.

MaxAgeSec=

MaxAgeSec specifies the number of seconds of maximum message age. If the last seen (received) hello packet is more than this number of seconds old, the bridge in question will start the takeover procedure in attempt to become the Root Bridge itself.

ForwardDelaySec=

ForwardDelaySec specifies the number of seconds spent in each of the Listening and Learning states before the Forwarding state is entered.

AgeingTimeSec=

This specifies the number of seconds a MAC Address will be kept in the forwarding database after having a packet received from this MAC Address.

Priority=

The priority of the bridge. An integer between 0 and 65535. A lower value means higher priority. The bridge having the lowest priority will be elected as root bridge.

GroupForwardMask=

A 16-bit bitmask represented as an integer which allows forwarding of link local frames with 802.1D reserved addresses (01:80:C2:00:00:0X). A logical AND is performed between the specified bitmask and the exponentiation of 2^X, the lower nibble of the last octet of the MAC address. For example, a value of 8 would allow forwarding of frames addressed to 01:80:C2:00:00:03 (802.1X PAE).

DefaultPVID=

This specifies the default port VLAN ID of a newly attached bridge port. Set this to an integer in the range 1...4094 or "none" to disable the PVID.

MulticastQuerier=

Takes a boolean. This setting controls the IFLA_BR_MCAST_QUERIER option in the kernel. If enabled, the kernel will send general ICMP queries from a zero source address. This feature should allow faster convergence on startup, but it causes some multicast-aware switches to misbehave and disrupt forwarding of multicast packets. When unset, the kernel's default will be used.

MulticastSnooping=

Takes a boolean. This setting controls the IFLA_BR_MCAST_SNOOPING option in the kernel. If enabled, IGMP snooping monitors the Internet Group Management Protocol (IGMP) traffic between hosts and multicast routers. When unset, the kernel's default will be used.

VLANFiltering=

Takes a boolean. This setting controls the IFLA_BR_VLAN_FILTERING option in the kernel. If enabled, the bridge will be started in VLAN-filtering mode. When unset, the kernel's default will be used.

VLANProtocol=

Allows setting the protocol used for VLAN filtering. Takes 802.1q or, 802.1ad, and defaults to unset and kernel's default is used.

STP=

Takes a boolean. This enables the bridge's Spanning Tree Protocol (STP). When unset, the kernel's default will be used.

MulticastIGMPVersion=

Allows changing bridge's multicast Internet Group Management Protocol (IGMP) version. Takes an integer 2 or 3. When unset, the kernel's default will be used.

## [VLAN] SECTION OPTIONS
The [VLAN] section only applies for netdevs of kind "vlan", and accepts the following key:

Id=

The VLAN ID to use. An integer in the range 0...4094. This setting is compulsory.

Protocol=

Allows setting the protocol used for the VLAN interface. Takes "802.1q" or, "802.1ad", and defaults to unset and kernel's default is used.

GVRP=

Takes a boolean. The Generic VLAN Registration Protocol (GVRP) is a protocol that allows automatic learning of VLANs on a network. When unset, the kernel's default will be used.

MVRP=

Takes a boolean. Multiple VLAN Registration Protocol (MVRP) formerly known as GARP VLAN Registration Protocol (GVRP) is a standards-based Layer 2 network protocol, for automatic configuration of VLAN information on switches. It was defined in the 802.1ak amendment to 802.1Q-2005. When unset, the kernel's default will be used.

LooseBinding=

Takes a boolean. The VLAN loose binding mode, in which only the operational state is passed from the parent to the associated VLANs, but the VLAN device state is not changed. When unset, the kernel's default will be used.

ReorderHeader=

Takes a boolean. When enabled, the VLAN reorder header is used and VLAN interfaces behave like physical interfaces. When unset, the kernel's default will be used.

EgressQOSMaps=

Defines a mapping of Linux internal packet priority (SO_PRIORITY) to VLAN header PCP field for outgoing frames. Takes a whitespace-separated list of unsigned integer pairs in the format "from"-"to", e.g., "21-7 45-5" ranges 1–4294967294. Note that "from" must be greater than or equal to "to". When unset, the kernel's default will be used.

IngressQOSMaps=

Defines a mapping of Linux internal packet priority (SO_PRIORITY) to VLAN header PCP field for incoming frames. Takes a whitespace-separated list of unsigned integer pairs in the format "from"-"to", e.g., "21-7 45-5" ranges 1–4294967294. Note that "from" must be greater than or equal to "to". When unset, the kernel's default will be used.

## [MACVLAN] SECTION OPTIONS
The [MACVLAN] section only applies for netdevs of kind "macvlan", and accepts the following key:

Mode=

The MACVLAN mode to use. The supported options are "private", "vepa", "bridge", "passthru", and "source".

SourceMACAddress=

A whitespace-separated list of remote hardware addresses allowed on the MACVLAN. This option only has an effect in source mode. Use full colon-, hyphen- or dot-delimited hexadecimal. This option may appear more than once, in which case the lists are merged. If the empty string is assigned to this option, the list of hardware addresses defined prior to this is reset. Defaults to unset.

BroadcastMulticastQueueLength=

Specifies the length of the receive queue for broadcast/multicast packets. An unsigned integer in the range 0...4294967294. Defaults to unset.

## [MACVTAP] SECTION OPTIONS
The [MACVTAP] section applies for netdevs of kind "macvtap" and accepts the same keys as [MACVLAN].

## [IPVLAN] SECTION OPTIONS
The [IPVLAN] section only applies for netdevs of kind "ipvlan", and accepts the following key:

Mode=

The IPVLAN mode to use. The supported options are "L2","L3" and "L3S".

Flags=

The IPVLAN flags to use. The supported options are "bridge","private" and "vepa".

## [IPVTAP] SECTION OPTIONS
The [IPVTAP] section only applies for netdevs of kind "ipvtap" and accepts the same keys as [IPVLAN].

## [VXLAN] SECTION OPTIONS
The [VXLAN] section only applies for netdevs of kind "vxlan", and accepts the following keys:

VNI=

The VXLAN Network Identifier (or VXLAN Segment ID). Takes a number in the range 1...16777215.

Remote=

Configures destination IP address.

Local=

Configures local IP address.

Group=

Configures VXLAN multicast group IP address. All members of a VXLAN must use the same multicast group address.

TOS=

The Type Of Service byte value for a vxlan interface.

TTL=

A fixed Time To Live N on Virtual eXtensible Local Area Network packets. Takes "inherit" or a number in the range 0...255. 0 is a special value meaning inherit the inner protocol's TTL value. "inherit" means that it will inherit the outer protocol's TTL value.

MacLearning=

Takes a boolean. When true, enables dynamic MAC learning to discover remote MAC addresses.

FDBAgeingSec=

The lifetime of Forwarding Database entry learnt by the kernel, in seconds.

MaximumFDBEntries=

Configures maximum number of FDB entries.

ReduceARPProxy=

Takes a boolean. When true, bridge-connected VXLAN tunnel endpoint answers ARP requests from the local bridge on behalf of remote Distributed Overlay Virtual Ethernet (DVOE)[6] clients. Defaults to false.

L2MissNotification=

Takes a boolean. When true, enables netlink LLADDR miss notifications.

L3MissNotification=

Takes a boolean. When true, enables netlink IP address miss notifications.

RouteShortCircuit=

Takes a boolean. When true, route short circuiting is turned on.

UDPChecksum=

Takes a boolean. When true, transmitting UDP checksums when doing VXLAN/IPv4 is turned on.

UDP6ZeroChecksumTx=

Takes a boolean. When true, sending zero checksums in VXLAN/IPv6 is turned on.

UDP6ZeroChecksumRx=

Takes a boolean. When true, receiving zero checksums in VXLAN/IPv6 is turned on.

RemoteChecksumTx=

Takes a boolean. When true, remote transmit checksum offload of VXLAN is turned on.

RemoteChecksumRx=

Takes a boolean. When true, remote receive checksum offload in VXLAN is turned on.

GroupPolicyExtension=

Takes a boolean. When true, it enables Group Policy VXLAN extension security label mechanism across network peers based on VXLAN. For details about the Group Policy VXLAN, see the VXLAN Group Policy[7] document. Defaults to false.

GenericProtocolExtension=

Takes a boolean. When true, Generic Protocol Extension extends the existing VXLAN protocol to provide protocol typing, OAM, and versioning capabilities. For details about the VXLAN GPE Header, see the Generic Protocol Extension for VXLAN[8] document. If destination port is not specified and Generic Protocol Extension is set then default port of 4790 is used. Defaults to false.

DestinationPort=

Configures the default destination UDP port. If the destination port is not specified then Linux kernel default will be used. Set to 4789 to get the IANA assigned value.

PortRange=

Configures the source port range for the VXLAN. The kernel assigns the source UDP port based on the flow to help the receiver to do load balancing. When this option is not set, the normal range of local UDP ports is used.

FlowLabel=

Specifies the flow label to use in outgoing packets. The valid range is 0-1048575.

IPDoNotFragment=

Allows setting the IPv4 Do not Fragment (DF) bit in outgoing packets, or to inherit its value from the IPv4 inner header. Takes a boolean value, or "inherit". Set to "inherit" if the encapsulated protocol is IPv6. When unset, the kernel's default will be used.

## [GENEVE] SECTION OPTIONS
The [GENEVE] section only applies for netdevs of kind "geneve", and accepts the following keys:

Id=

Specifies the Virtual Network Identifier (VNI) to use, a number between 0 and 16777215. This field is mandatory.

Remote=

Specifies the unicast destination IP address to use in outgoing packets.

TOS=

Specifies the TOS value to use in outgoing packets. Takes a number between 1 and 255.

TTL=

Accepts the same values as in the [VXLAN] section, except that when unset or set to 0, the kernel's default will be used, meaning that packet TTL will be set from /proc/sys/net/ipv4/ip_default_ttl.

UDPChecksum=

Takes a boolean. When true, specifies that UDP checksum is calculated for transmitted packets over IPv4.

UDP6ZeroChecksumTx=

Takes a boolean. When true, skip UDP checksum calculation for transmitted packets over IPv6.

UDP6ZeroChecksumRx=

Takes a boolean. When true, allows incoming UDP packets over IPv6 with zero checksum field.

DestinationPort=

Specifies destination port. Defaults to 6081. If not set or assigned the empty string, the default port of 6081 is used.

FlowLabel=

Specifies the flow label to use in outgoing packets.

IPDoNotFragment=

Accepts the same key as in [VXLAN] section.

Independent=

Takes a boolean. When true, the vxlan interface is created without any underlying network interface. Defaults to false, which means that a .network file that requests this tunnel using Tunnel= is required for the tunnel to be created.

## [BAREUDP] SECTION OPTIONS
The [BareUDP] section only applies for netdevs of kind "bareudp", and accepts the following keys:

DestinationPort=

Specifies the destination UDP port (in range 1...65535). This is mandatory.

EtherType=

Specifies the L3 protocol. Takes one of "ipv4", "ipv6", "mpls-uc" or "mpls-mc". This is mandatory.

## [L2TP] SECTION OPTIONS
The [L2TP] section only applies for netdevs of kind "l2tp", and accepts the following keys:

TunnelId=

Specifies the tunnel identifier. Takes an number in the range 1...4294967295. The value used must match the "PeerTunnelId=" value being used at the peer. This setting is compulsory.

PeerTunnelId=

Specifies the peer tunnel id. Takes a number in the range 1...4294967295. The value used must match the "TunnelId=" value being used at the peer. This setting is compulsory.

Remote=

Specifies the IP address of the remote peer. This setting is compulsory.

Local=

Specifies the IP address of the local interface. Takes an IP address, or the special values "auto", "static", or "dynamic". When an address is set, then the local interface must have the address. If "auto", then one of the addresses on the local interface is used. Similarly, if "static" or "dynamic" is set, then one of the static or dynamic addresses on the local interface is used. Defaults to "auto".

EncapsulationType=

Specifies the encapsulation type of the tunnel. Takes one of "udp" or "ip".

UDPSourcePort=

Specifies the UDP source port to be used for the tunnel. When UDP encapsulation is selected it's mandatory. Ignored when IP encapsulation is selected.

UDPDestinationPort=

Specifies destination port. When UDP encapsulation is selected it's mandatory. Ignored when IP encapsulation is selected.

UDPChecksum=

Takes a boolean. When true, specifies that UDP checksum is calculated for transmitted packets over IPv4.

UDP6ZeroChecksumTx=

Takes a boolean. When true, skip UDP checksum calculation for transmitted packets over IPv6.

UDP6ZeroChecksumRx=

Takes a boolean. When true, allows incoming UDP packets over IPv6 with zero checksum field.

## [L2TPSESSION] SECTION OPTIONS
The [L2TPSession] section only applies for netdevs of kind "l2tp", and accepts the following keys:

Name=

Specifies the name of the session. This setting is compulsory.

SessionId=

Specifies the session identifier. Takes an number in the range 1...4294967295. The value used must match the "SessionId=" value being used at the peer. This setting is compulsory.

PeerSessionId=

Specifies the peer session identifier. Takes an number in the range 1...4294967295. The value used must match the "PeerSessionId=" value being used at the peer. This setting is compulsory.

Layer2SpecificHeader=

Specifies layer2specific header type of the session. One of "none" or "default". Defaults to "default".

## [MACSEC] SECTION OPTIONS
The [MACsec] section only applies for network devices of kind "macsec", and accepts the following keys:

Port=

Specifies the port to be used for the MACsec transmit channel. The port is used to make secure channel identifier (SCI). Takes a value between 1 and 65535. Defaults to unset.

Encrypt=

Takes a boolean. When true, enable encryption. Defaults to unset.

## [MACSECRECEIVECHANNEL] SECTION OPTIONS
The [MACsecReceiveChannel] section only applies for network devices of kind "macsec", and accepts the following keys:

Port=

Specifies the port to be used for the MACsec receive channel. The port is used to make secure channel identifier (SCI). Takes a value between 1 and 65535. This option is compulsory, and is not set by default.

MACAddress=

Specifies the MAC address to be used for the MACsec receive channel. The MAC address used to make secure channel identifier (SCI). This setting is compulsory, and is not set by default.

## [MACSECTRANSMITASSOCIATION] SECTION OPTIONS
The [MACsecTransmitAssociation] section only applies for network devices of kind "macsec", and accepts the following keys:

PacketNumber=

Specifies the packet number to be used for replay protection and the construction of the initialization vector (along with the secure channel identifier [SCI]). Takes a value between 1-4,294,967,295. Defaults to unset.

KeyId=

Specifies the identification for the key. Takes a number between 0-255. This option is compulsory, and is not set by default.

Key=

Specifies the encryption key used in the transmission channel. The same key must be configured on the peer’s matching receive channel. This setting is compulsory, and is not set by default. Takes a 128-bit key encoded in a hexadecimal string, for example "dffafc8d7b9a43d5b9a3dfbbf6a30c16".

KeyFile=

Takes an absolute path to a file which contains a 128-bit key encoded in a hexadecimal string, which will be used in the transmission channel. When this option is specified, Key= is ignored. Note that the file must be readable by the user "systemd-network", so it should be, e.g., owned by "root:systemd-network" with a "0640" file mode. If the path refers to an AF_UNIX stream socket in the file system a connection is made to it and the key read from it.

Activate=

Takes a boolean. If enabled, then the security association is activated. Defaults to unset.

UseForEncoding=

Takes a boolean. If enabled, then the security association is used for encoding. Only one [MACsecTransmitAssociation] section can enable this option. When enabled, Activate=yes is implied. Defaults to unset.

## [MACSECRECEIVEASSOCIATION] SECTION OPTIONS
The [MACsecReceiveAssociation] section only applies for network devices of kind "macsec", and accepts the following keys:

Port=

Accepts the same key as in [MACsecReceiveChannel] section.

MACAddress=

Accepts the same key as in [MACsecReceiveChannel] section.

PacketNumber=

Accepts the same key as in [MACsecTransmitAssociation] section.

KeyId=

Accepts the same key as in [MACsecTransmitAssociation] section.

Key=

Accepts the same key as in [MACsecTransmitAssociation] section.

KeyFile=

Accepts the same key as in [MACsecTransmitAssociation] section.

Activate=

Accepts the same key as in [MACsecTransmitAssociation] section.

## [TUNNEL] SECTION OPTIONS
The [Tunnel] section only applies for netdevs of kind "ipip", "sit", "gre", "gretap", "ip6gre", "ip6gretap", "vti", "vti6", "ip6tnl", and "erspan" and accepts the following keys:

Local=

A static local address for tunneled packets. It must be an address on another interface of this host, or the special value "any".

Remote=

The remote endpoint of the tunnel. Takes an IP address or the special value "any".

TOS=

The Type Of Service byte value for a tunnel interface. For details about the TOS, see the Type of Service in the Internet Protocol Suite[9] document.

TTL=

A fixed Time To Live N on tunneled packets. N is a number in the range 1...255. 0 is a special value meaning that packets inherit the TTL value. The default value for IPv4 tunnels is 0 (inherit). The default value for IPv6 tunnels is 64.

DiscoverPathMTU=

Takes a boolean. When true, enables Path MTU Discovery on the tunnel.

IPv6FlowLabel=

Configures the 20-bit flow label (see RFC 6437[10]) field in the IPv6 header (see RFC 2460[11]), which is used by a node to label packets of a flow. It is only used for IPv6 tunnels. A flow label of zero is used to indicate packets that have not been labeled. It can be configured to a value in the range 0...0xFFFFF, or be set to "inherit", in which case the original flowlabel is used.

CopyDSCP=

Takes a boolean. When true, the Differentiated Service Code Point (DSCP) field will be copied to the inner header from outer header during the decapsulation of an IPv6 tunnel packet. DSCP is a field in an IP packet that enables different levels of service to be assigned to network traffic. Defaults to "no".

EncapsulationLimit=

The Tunnel Encapsulation Limit option specifies how many additional levels of encapsulation are permitted to be prepended to the packet. For example, a Tunnel Encapsulation Limit option containing a limit value of zero means that a packet carrying that option may not enter another tunnel before exiting the current tunnel. (see RFC 2473[12]). The valid range is 0–255 and "none". Defaults to 4.

Key=

The Key= parameter specifies the same key to use in both directions (InputKey= and OutputKey=). The Key= is either a number or an IPv4 address-like dotted quad. It is used as mark-configured SAD/SPD entry as part of the lookup key (both in data and control path) in IP XFRM (framework used to implement IPsec protocol). See ip-xfrm — transform configuration[13] for details. It is only used for VTI/VTI6, GRE, GRETAP, and ERSPAN tunnels.

InputKey=

The InputKey= parameter specifies the key to use for input. The format is same as Key=. It is only used for VTI/VTI6, GRE, GRETAP, and ERSPAN tunnels.

OutputKey=

The OutputKey= parameter specifies the key to use for output. The format is same as Key=. It is only used for VTI/VTI6, GRE, GRETAP, and ERSPAN tunnels.

Mode=

An "ip6tnl" tunnel can be in one of three modes "ip6ip6" for IPv6 over IPv6, "ipip6" for IPv4 over IPv6 or "any" for either.

Independent=

Takes a boolean. When false (the default), the tunnel is always created over some network device, and a .network file that requests this tunnel using Tunnel= is required for the tunnel to be created. When true, the tunnel is created independently of any network as "tunnel@NONE".

AssignToLoopback=

Takes a boolean. If set to "yes", the loopback interface "lo" is used as the underlying device of the tunnel interface. Defaults to "no".

AllowLocalRemote=

Takes a boolean. When true allows tunnel traffic on ip6tnl devices where the remote endpoint is a local host address. When unset, the kernel's default will be used.

FooOverUDP=

Takes a boolean. Specifies whether FooOverUDP= tunnel is to be configured. Defaults to false. This takes effects only for IPIP, SIT, GRE, and GRETAP tunnels. For more detail information see Foo over UDP[14]

FOUDestinationPort=

This setting specifies the UDP destination port for encapsulation. This field is mandatory when FooOverUDP=yes, and is not set by default.

FOUSourcePort=

This setting specifies the UDP source port for encapsulation. Defaults to 0 — that is, the source port for packets is left to the network stack to decide.

Encapsulation=

Accepts the same key as in the [FooOverUDP] section.

IPv6RapidDeploymentPrefix=

Reconfigure the tunnel for IPv6 Rapid Deployment[15], also known as 6rd. The value is an ISP-specific IPv6 prefix with a non-zero length. Only applicable to SIT tunnels.

ISATAP=

Takes a boolean. If set, configures the tunnel as Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) tunnel. Only applicable to SIT tunnels. When unset, the kernel's default will be used.

SerializeTunneledPackets=

Takes a boolean. If set to yes, then packets are serialized. Only applies for GRE, GRETAP, and ERSPAN tunnels. When unset, the kernel's default will be used.

ERSPANIndex=

Specifies the ERSPAN index field for the interface, an integer in the range 1...1048575 associated with the ERSPAN traffic's source port and direction. This field is mandatory.

## [FOOOVERUDP] SECTION OPTIONS
The [FooOverUDP] section only applies for netdevs of kind "fou" and accepts the following keys:

Encapsulation=

Specifies the encapsulation mechanism used to store networking packets of various protocols inside the UDP packets. Supports the following values: "FooOverUDP" provides the simplest no-frills model of UDP encapsulation, it simply encapsulates packets directly in the UDP payload. "GenericUDPEncapsulation" is a generic and extensible encapsulation, it allows encapsulation of packets for any IP protocol and optional data as part of the encapsulation. For more detailed information see Generic UDP Encapsulation[16]. Defaults to "FooOverUDP".

Port=

Specifies the port number where the encapsulated packets will arrive. Those packets will be removed and manually fed back into the network stack with the encapsulation removed to be sent to the real destination. This option is mandatory.

PeerPort=

Specifies the peer port number. Defaults to unset. Note that when peer port is set "Peer=" address is mandatory.

Protocol=

The Protocol= specifies the protocol number of the packets arriving at the UDP port. When Encapsulation=FooOverUDP, this field is mandatory and is not set by default. Takes an IP protocol name such as "gre" or "ipip", or an integer within the range 1...255. When Encapsulation=GenericUDPEncapsulation, this must not be specified.

Peer=

Configures peer IP address. Note that when peer address is set "PeerPort=" is mandatory.

Local=

Configures local IP address.

## [PEER] SECTION OPTIONS
The [Peer] section only applies for netdevs of kind "veth" and accepts the following keys:

Name=

The interface name used when creating the netdev. This setting is compulsory.

MACAddress=

The peer MACAddress, if not set, it is generated in the same way as the MAC address of the main interface.

## [VXCAN] SECTION OPTIONS
The [VXCAN] section only applies for netdevs of kind "vxcan" and accepts the following key:

Peer=

The peer interface name used when creating the netdev. This setting is compulsory.

## [TUN] SECTION OPTIONS
The [Tun] section only applies for netdevs of kind "tun", and accepts the following keys:

MultiQueue=

Takes a boolean. Configures whether to use multiple file descriptors (queues) to parallelize packets sending and receiving. Defaults to "no".

PacketInfo=

Takes a boolean. Configures whether packets should be prepended with four extra bytes (two flag bytes and two protocol bytes). If disabled, it indicates that the packets will be pure IP packets. Defaults to "no".

VNetHeader=

Takes a boolean. Configures IFF_VNET_HDR flag for a tun or tap device. It allows sending and receiving larger Generic Segmentation Offload (GSO) packets. This may increase throughput significantly. Defaults to "no".

User=

User to grant access to the /dev/net/tun device.

Group=

Group to grant access to the /dev/net/tun device.

## [TAP] SECTION OPTIONS
The [Tap] section only applies for netdevs of kind "tap", and accepts the same keys as the [Tun] section.

## [WIREGUARD] SECTION OPTIONS
The [WireGuard] section accepts the following keys:

PrivateKey=

The Base64 encoded private key for the interface. It can be generated using the wg genkey command (see wg(8)). This option or PrivateKeyFile= is mandatory to use WireGuard. Note that because this information is secret, you may want to set the permissions of the .netdev file to be owned by "root:systemd-network" with a "0640" file mode.

PrivateKeyFile=

Takes an absolute path to a file which contains the Base64 encoded private key for the interface. When this option is specified, then PrivateKey= is ignored. Note that the file must be readable by the user "systemd-network", so it should be, e.g., owned by "root:systemd-network" with a "0640" file mode. If the path refers to an AF_UNIX stream socket in the file system a connection is made to it and the key read from it.

ListenPort=

Sets UDP port for listening. Takes either value between 1 and 65535 or "auto". If "auto" is specified, the port is automatically generated based on interface name. Defaults to "auto".

FirewallMark=

Sets a firewall mark on outgoing WireGuard packets from this interface. Takes a number between 1 and 4294967295.

## [WIREGUARDPEER] SECTION OPTIONS
The [WireGuardPeer] section accepts the following keys:

PublicKey=

Sets a Base64 encoded public key calculated by wg pubkey (see wg(8)) from a private key, and usually transmitted out of band to the author of the configuration file. This option is mandatory for this section.

PresharedKey=

Optional preshared key for the interface. It can be generated by the wg genpsk command. This option adds an additional layer of symmetric-key cryptography to be mixed into the already existing public-key cryptography, for post-quantum resistance. Note that because this information is secret, you may want to set the permissions of the .netdev file to be owned by "root:systemd-network" with a "0640" file mode.

PresharedKeyFile=

Takes an absolute path to a file which contains the Base64 encoded preshared key for the peer. When this option is specified, then PresharedKey= is ignored. Note that the file must be readable by the user "systemd-network", so it should be, e.g., owned by "root:systemd-network" with a "0640" file mode. If the path refers to an AF_UNIX stream socket in the file system a connection is made to it and the key read from it.

AllowedIPs=

Sets a comma-separated list of IP (v4 or v6) addresses with CIDR masks from which this peer is allowed to send incoming traffic and to which outgoing traffic for this peer is directed. The catch-all 0.0.0.0/0 may be specified for matching all IPv4 addresses, and ::/0 may be specified for matching all IPv6 addresses.

Note that this only affects routing inside the network interface itself, i.e. the packets that pass through the tunnel itself. To cause packets to be sent via the tunnel in the first place, an appropriate route needs to be added as well — either in the "[Routes]" section on the ".network" matching the wireguard interface, or externally to systemd-networkd.

Endpoint=

Sets an endpoint IP address or hostname, followed by a colon, and then a port number. This endpoint will be updated automatically once to the most recent source IP address and port of correctly authenticated packets from the peer at configuration time.

PersistentKeepalive=

Sets a seconds interval, between 1 and 65535 inclusive, of how often to send an authenticated empty packet to the peer for the purpose of keeping a stateful firewall or NAT mapping valid persistently. For example, if the interface very rarely sends traffic, but it might at anytime receive traffic from a peer, and it is behind NAT, the interface might benefit from having a persistent keepalive interval of 25 seconds. If set to 0 or "off", this option is disabled. By default or when unspecified, this option is off. Most users will not need this.

## [BOND] SECTION OPTIONS
The [Bond] section accepts the following key:

Mode=

Specifies one of the bonding policies. The default is "balance-rr" (round robin). Possible values are "balance-rr", "active-backup", "balance-xor", "broadcast", "802.3ad", "balance-tlb", and "balance-alb".

TransmitHashPolicy=

Selects the transmit hash policy to use for slave selection in balance-xor, 802.3ad, and tlb modes. Possible values are "layer2", "layer3+4", "layer2+3", "encap2+3", and "encap3+4".

LACPTransmitRate=

Specifies the rate with which link partner transmits Link Aggregation Control Protocol Data Unit packets in 802.3ad mode. Possible values are "slow", which requests partner to transmit LACPDUs every 30 seconds, and "fast", which requests partner to transmit LACPDUs every second. The default value is "slow".

MIIMonitorSec=

Specifies the frequency that Media Independent Interface link monitoring will occur. A value of zero disables MII link monitoring. This value is rounded down to the nearest millisecond. The default value is 0.

UpDelaySec=

Specifies the delay before a link is enabled after a link up status has been detected. This value is rounded down to a multiple of MIIMonitorSec. The default value is 0.

DownDelaySec=

Specifies the delay before a link is disabled after a link down status has been detected. This value is rounded down to a multiple of MIIMonitorSec. The default value is 0.

LearnPacketIntervalSec=

Specifies the number of seconds between instances where the bonding driver sends learning packets to each slave peer switch. The valid range is 1–0x7fffffff; the default value is 1. This option has an effect only for the balance-tlb and balance-alb modes.

AdSelect=

Specifies the 802.3ad aggregation selection logic to use. Possible values are "stable", "bandwidth" and "count".

AdActorSystemPriority=

Specifies the 802.3ad actor system priority. Takes a number in the range 1...65535.

AdUserPortKey=

Specifies the 802.3ad user defined portion of the port key. Takes a number in the range 0...1023.

AdActorSystem=

Specifies the 802.3ad system MAC address. This cannot be a null or multicast address.

FailOverMACPolicy=

Specifies whether the active-backup mode should set all slaves to the same MAC address at the time of enslavement or, when enabled, to perform special handling of the bond's MAC address in accordance with the selected policy. The default policy is none. Possible values are "none", "active" and "follow".

ARPValidate=

Specifies whether or not ARP probes and replies should be validated in any mode that supports ARP monitoring, or whether non-ARP traffic should be filtered (disregarded) for link monitoring purposes. Possible values are "none", "active", "backup" and "all".

ARPIntervalSec=

Specifies the ARP link monitoring frequency. A value of 0 disables ARP monitoring. The default value is 0, and the default unit seconds.

ARPIPTargets=

Specifies the IP addresses to use as ARP monitoring peers when ARPIntervalSec is greater than 0. These are the targets of the ARP request sent to determine the health of the link to the targets. Specify these values in IPv4 dotted decimal format. At least one IP address must be given for ARP monitoring to function. The maximum number of targets that can be specified is 16. The default value is no IP addresses.

ARPAllTargets=

Specifies the quantity of ARPIPTargets that must be reachable in order for the ARP monitor to consider a slave as being up. This option affects only active-backup mode for slaves with ARPValidate enabled. Possible values are "any" and "all".

PrimaryReselectPolicy=

Specifies the reselection policy for the primary slave. This affects how the primary slave is chosen to become the active slave when failure of the active slave or recovery of the primary slave occurs. This option is designed to prevent flip-flopping between the primary slave and other slaves. Possible values are "always", "better" and "failure".

ResendIGMP=

Specifies the number of IGMP membership reports to be issued after a failover event. One membership report is issued immediately after the failover, subsequent packets are sent in each 200ms interval. The valid range is 0–255. Defaults to 1. A value of 0 prevents the IGMP membership report from being issued in response to the failover event.

PacketsPerSlave=

Specify the number of packets to transmit through a slave before moving to the next one. When set to 0, then a slave is chosen at random. The valid range is 0–65535. Defaults to 1. This option only has effect when in balance-rr mode.

GratuitousARP=

Specify the number of peer notifications (gratuitous ARPs and unsolicited IPv6 Neighbor Advertisements) to be issued after a failover event. As soon as the link is up on the new slave, a peer notification is sent on the bonding device and each VLAN sub-device. This is repeated at each link monitor interval (ARPIntervalSec or MIIMonitorSec, whichever is active) if the number is greater than 1. The valid range is 0–255. The default value is 1. These options affect only the active-backup mode.

AllSlavesActive=

Takes a boolean. Specifies that duplicate frames (received on inactive ports) should be dropped when false, or delivered when true. Normally, bonding will drop duplicate frames (received on inactive ports), which is desirable for most users. But there are some times it is nice to allow duplicate frames to be delivered. The default value is false (drop duplicate frames received on inactive ports).

DynamicTransmitLoadBalancing=

Takes a boolean. Specifies if dynamic shuffling of flows is enabled. Applies only for balance-tlb mode. Defaults to unset.

MinLinks=

Specifies the minimum number of links that must be active before asserting carrier. The default value is 0.

For more detail information see Linux Ethernet Bonding Driver HOWTO[1]

## [XFRM] SECTION OPTIONS
The [Xfrm] section accepts the following keys:

InterfaceId=

Sets the ID/key of the xfrm interface which needs to be associated with a SA/policy. Can be decimal or hexadecimal, valid range is 1-0xffffffff. This is mandatory.

Independent=

Takes a boolean. If false (the default), the xfrm interface must have an underlying device which can be used for hardware offloading.

For more detail information see Virtual XFRM Interfaces[17].

## [VRF] SECTION OPTIONS
The [VRF] section only applies for netdevs of kind "vrf" and accepts the following key:

Table=

The numeric routing table identifier. This setting is compulsory.

## [BATMANADVANCED] SECTION OPTIONS
The [BatmanAdvanced] section only applies for netdevs of kind "batadv" and accepts the following keys:

GatewayMode=

Takes one of "off", "server", or "client". A batman-adv node can either run in server mode (sharing its internet connection with the mesh) or in client mode (searching for the most suitable internet connection in the mesh) or having the gateway support turned off entirely (which is the default setting).

Aggregation=

Takes a boolean value. Enables or disables aggregation of originator messages. Defaults to true.

BridgeLoopAvoidance=

Takes a boolean value. Enables or disables avoidance of loops on bridges. Defaults to true.

DistributedArpTable=

Takes a boolean value. Enables or disables the distributed ARP table. Defaults to true.

Fragmentation=

Takes a boolean value. Enables or disables fragmentation. Defaults to true.

HopPenalty=

The hop penalty setting allows to modify batctl(8) preference for multihop routes vs. short routes. This integer value is applied to the TQ (Transmit Quality) of each forwarded OGM (Originator Message), thereby propagating the cost of an extra hop (the packet has to be received and retransmitted which costs airtime). A higher hop penalty will make it more unlikely that other nodes will choose this node as intermediate hop towards any given destination. The default hop penalty of '15' is a reasonable value for most setups and probably does not need to be changed. However, mobile nodes could choose a value of 255 (maximum value) to avoid being chosen as a router by other nodes. The minimum value is 0.

OriginatorIntervalSec=

The value specifies the interval in seconds, unless another time unit is specified in which batman-adv floods the network with its protocol information. See systemd.time(7) for more information.

GatewayBandwidthDown=

If the node is a server, this parameter is used to inform other nodes in the network about this node's internet connection download bandwidth in bits per second. Just enter any number suffixed with K, M, G or T (base 1000) and the batman-adv module will propagate the entered value in the mesh.

GatewayBandwidthUp=

If the node is a server, this parameter is used to inform other nodes in the network about this node's internet connection upload bandwidth in bits per second. Just enter any number suffixed with K, M, G or T (base 1000) and the batman-adv module will propagate the entered value in the mesh.

RoutingAlgorithm=

This can be either "batman-v" or "batman-iv" and describes which routing_algo of batctl(8) to use. The algorithm cannot be changed after interface creation. Defaults to "batman-v".

## EXAMPLES
Example 1. /etc/systemd/network/25-bridge.netdev

```
[NetDev]
Name=bridge0
Kind=bridge
```

Example 2. /etc/systemd/network/25-vlan1.netdev

```
[Match]
Virtualization=no
[NetDev]
Name=vlan1
Kind=vlan
[VLAN]
Id=1
```

Example 3. /etc/systemd/network/25-ipip.netdev

```
[NetDev]
Name=ipip-tun
Kind=ipip
MTUBytes=1480
[Tunnel]
Local=192.168.223.238
Remote=192.169.224.239
TTL=64
```

Example 4. /etc/systemd/network/1-fou-tunnel.netdev

```
[NetDev]
Name=fou-tun
Kind=fou
[FooOverUDP]
Port=5555
Protocol=4

```

Example 5. /etc/systemd/network/25-fou-ipip.netdev

```
[NetDev]
Name=ipip-tun
Kind=ipip
[Tunnel]
Independent=yes
Local=10.65.208.212
Remote=10.65.208.211
FooOverUDP=yes
FOUDestinationPort=5555

```

Example 6. /etc/systemd/network/25-tap.netdev

```
[NetDev]
Name=tap-test
Kind=tap
[Tap]
MultiQueue=yes
PacketInfo=yes
```

Example 7. /etc/systemd/network/25-sit.netdev

```
[NetDev]
Name=sit-tun
Kind=sit
MTUBytes=1480
[Tunnel]
Local=10.65.223.238
Remote=10.65.223.239
```

Example 8. /etc/systemd/network/25-6rd.netdev

```
[NetDev]
Name=6rd-tun
Kind=sit
MTUBytes=1480
[Tunnel]
Local=10.65.223.238
IPv6RapidDeploymentPrefix=2602::/24
```

Example 9. /etc/systemd/network/25-gre.netdev

```
[NetDev]
Name=gre-tun
Kind=gre
MTUBytes=1480
[Tunnel]
Local=10.65.223.238
Remote=10.65.223.239
```

Example 10. /etc/systemd/network/25-ip6gre.netdev

```
[NetDev]
Name=ip6gre-tun
Kind=ip6gre
[Tunnel]
Key=123
```

Example 11. /etc/systemd/network/25-vti.netdev

```
[NetDev]
Name=vti-tun
Kind=vti
MTUBytes=1480
[Tunnel]
Local=10.65.223.238
Remote=10.65.223.239
```

Example 12. /etc/systemd/network/25-veth.netdev

```
[NetDev]
Name=veth-test
Kind=veth
[Peer]
Name=veth-peer
```

Example 13. /etc/systemd/network/25-bond.netdev

```
[NetDev]
Name=bond1
Kind=bond
[Bond]
Mode=802.3ad
TransmitHashPolicy=layer3+4
MIIMonitorSec=1s
LACPTransmitRate=fast
```

Example 14. /etc/systemd/network/25-dummy.netdev

```
[NetDev]
Name=dummy-test
Kind=dummy
MACAddress=12:34:56:78:9a:bc
```

Example 15. /etc/systemd/network/25-vrf.netdev

Create a VRF interface with table 42.

```
[NetDev]
Name=vrf-test
Kind=vrf
[VRF]
Table=42
```

Example 16. /etc/systemd/network/25-macvtap.netdev

Create a MacVTap device.

```
[NetDev]
Name=macvtap-test
Kind=macvtap

```

Example 17. /etc/systemd/network/25-wireguard.netdev

```
[NetDev]
Name=wg0
Kind=wireguard
[WireGuard]
PrivateKey=EEGlnEPYJV//kbvvIqxKkQwOiS+UENyPncC4bF46ong=
ListenPort=51820
[WireGuardPeer]
PublicKey=RDf+LSpeEre7YEIKaxg+wbpsNV7du+ktR99uBEtIiCA=
AllowedIPs=fd31:bf08:57cb::/48,192.168.26.0/24
Endpoint=wireguard.example.com:51820
```

Example 18. /etc/systemd/network/27-xfrm.netdev

```
[NetDev]
Name=xfrm0
Kind=xfrm
[Xfrm]
Independent=yes
```

## SEE ALSO
systemd(1), systemd-networkd(8), systemd.link(5), systemd.network(5)

## NOTES
1.

Linux Ethernet Bonding Driver HOWTO

https://www.kernel.org/doc/Documentation/networking/bonding.txt

2.

RFC 2784

https://tools.ietf.org/html/rfc2784

3.

IEEE 802.1Q

http://www.ieee802.org/1/pages/802.1Q.html

4.

VRF

https://www.kernel.org/doc/Documentation/networking/vrf.txt

5.

B.A.T.M.A.N. Advanced

https://www.open-mesh.org/projects/open-mesh/wiki

6.

(DVOE)

https://en.wikipedia.org/wiki/Distributed_Overlay_Virtual_Ethernet

7.

VXLAN Group Policy

https://tools.ietf.org/html/draft-smith-vxlan-group-policy

8.

Generic Protocol Extension for VXLAN

https://tools.ietf.org/html/draft-ietf-nvo3-vxlan-gpe-07

9.

Type of Service in the Internet Protocol Suite

http://tools.ietf.org/html/rfc1349

10.

RFC 6437

https://tools.ietf.org/html/rfc6437

11.

RFC 2460

https://tools.ietf.org/html/rfc2460

12.

RFC 2473

https://tools.ietf.org/html/rfc2473#section-4.1.1

13.

ip-xfrm — transform configuration

http://man7.org/linux/man-pages/man8/ip-xfrm.8.html

14.

Foo over UDP

https://lwn.net/Articles/614348

15.

IPv6 Rapid Deployment

https://tools.ietf.org/html/rfc5569

16.

Generic UDP Encapsulation

https://lwn.net/Articles/615044

17.

Virtual XFRM Interfaces

https://lwn.net/Articles/757391